The present invention is concerned with an antiskid control system of the type wherein a sensor device monitors the rotational speed of a vehicle wheel to obtain control signals by which an electronic evaluation circuit is able to determine behavioral characteristics of the sensed wheel for the purpose of controlling modulator valves in the brake pressure line in order to regulate brake pressure in accordance with the dynamic wheel condition and accordingly ensure optimum braking.
Known systems of the above type employ a rotor whose teeth are sensed by a sensor device to generate output pulses having a repetition frequency proportional to the speed of rotation of the rotor and thus of the wheel with which the rotor is associated; a converter circuit which produces a d.c. voltage whose amplitude is proportional to the pulse frequency; a differentiator which forms acceleration control signals from the d.c. voltage and a logic circuit which evaluates these control signals in order to properly control the system modulator valves. The system further employs a logarithmic stage between the converter circuit and the differentiator. Since the quantity of the output d.c. voltage of the converter circuit is inversely proportional to the sensor output signal frequency, the logarithmic stage is required to simulate the angular wheel acceleration being monitored. However, when employing digital techniques, the cycle durations of the sensor output signals are not utilized directly but only via conversion to a d.c. voltage, with subsequent logarithmation and differentiation. Accordingly, not only do considerable sources of errors exist, but also considerable expense is entailed when attempting to use such a system in actual practice.